Method for making optical fibre fusion splice

ABSTRACT

When effecting a fusion splice between two optical fibres, end parts of the two fibres are introduced transversely into opposite ends of an open-ended channel 3 in a surface 2 of a rigid elongate support member 1 having at a position intermediate of its ends and in the surface a transversely extending open-ended slot 4 for temporarily accommodating the electrodes by which fusion splicing is to be effected. After fusion splicing of the fibres and withdrawal of the electrodes, any space in the channel 3 not occupied by the fusion spliced fibres and the transversely extending slot 4 are filled with a curable material which is permitted or caused to set. A preformed elongate lid 7 is secured to the surface 2 of the support member 1 and the support member and lid provide permanent protection for the fusion splice. &lt;IMAGE&gt;

This invention relates to end-to-end fusion splicing of optical fibres.

Many techniques differing from one another have been proposed foreffecting an end-to-end fusion splice between two optical fibres. Anideal fusion splicing technique should be capable of being readily usedin the field by a semi-skilled operator and should reliably andrepeatedly produce at any location satisfactory fusion splices.

It is an object of the present invention to provide an improved methodof effecting an end-to-end fusion splice between two optical fibres,which improved method can be readily and repeatedly effected andsubstantially reduces the risk that a unsatisfactory fusion splice willbe made.

In the improved method according to the invention, end parts of the twooptical fibres are introduced transversely into opposite end parts of anopen-ended channel in and extending throughout the length of a surfaceof a preformed substantially rigid elongate support member so that, at aposition intermediate of the ends of the support member, the end facesof the optical fibres abut or are spaced a short distance apart, thesupport member being made of a material which is capable of withstandingthe temperature to which it will be subjected during fusion splicing ofthe fibres and which will have no deleterious effect on the fibres andthe support member having at said position intermediate of its ends atransversely extending open-ended slot in said surface or transverselyopposed apertures opening into said channel for temporarilyaccommodating the electrodes by which fusion splicing is to be effected;the electrodes are introduced into said transversely extending slot ortransversely opposed apertures and fusion splicing of the adjacent endsof the optical fibres is effected; and, after fusion splicing of theoptical fibres has been effected and the electrodes have been withdrawn,any space in the channel not occupied by the fusion spliced opticalfibres and the transversely extending slot or transversely opposedapertures are substantially filled with a curable material in a liquidor semi-liquid state and the curable material is permitted or caused toset.

By virtue of the fact that the end part of each optical fibre isintroduced transversely into the open-ended channel in a surface of thesupport member, there is negligible risk of any damage being effected tothe end face of the fibre after the fibre has been cleaved and beforefusion splicing of the optical fibres is effected. Furthermore, inaddition to providing support for the aligned end parts of the opticalfibres during the fusion splicing operation, the rigid elongate memberalso provides permanent protection for the fusion splice between theoptical fibres.

After any space in the channel has been substantially filled withcurable material in a liquid or semi-liquid state, preferably apreformed elongate lid is secured to that surface of the support memberin which the channel lies. The preformed elongate lid may be made of thesame material as the elongate support member. If desired, the preformedlid may be temporarily applied to said surface of the support memberafter the optical fibres have been introduced into the channel andbefore fusion splicing is effected to assist in retaining the opticalfibres in the channel during fusion splicing.

Preferably, the preformed substantially rigid elongate support member ismade of a ceramic, vitreous or sintered material.

The open-ended channel in a surface of the elongate support member maybe of any transverse cross-section suitable for accommodating alignedoptical fibres. Preferred cross-sectional shapes include V-,U-and squarecross-sectional shapes.

Suitable curable materials that may be employed include an adhesivewhich is cured by ultra-violet radiation and a hot melt adhesive whichsets on cooling.

The invention also includes, for use in the improved method ashereinbefore described, a two-part component comprising a preformedsubstantially rigid elongate support member and an associated preformedelongate lid as hereinbefore described.

The invention is further illustrated by a description, by way ofexample, of four preferred forms of two-part component for use ineffecting an end-to-end fusion splice between two optical fibres and ofthe improved method of effecting an end-to-end fusion splice between twooptical fibres with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2, respectively, are an exploded isometric view and an endview of a first preferred form of two-part component, and

FIGS. 3 to 5 are end views of three alternative preferred forms oftwo-part component.

Referring to FIGS. 1 and 2, the first preferred form of two-partcomponent comprises a preformed rigid elongate support member 1 and,associated with the support member, a preformed elongate lid 7separately formed with respect to the support member. The elongatesupport member 1 has in one major surface 2 an open-ended channel 3 ofV-shaped cross-section extending throughout the length of the memberCentrally disposed between the ends of the support member 1 is atransversely extending open-ended slot 4 of rectangular cross-sectionfor temporarily accommodating electrodes by which fusion splicing of twooptical fibres which have been introduced transversely into the oppositeend parts of the open-ended channel 3 with their end faces disposed inthe transversely extending slot 4 and spaced a short distance apart. Theassociated preformed elongate lid 7 for closing the channel 3 in themajor surface 2 of the support member 1 has on its inner major surface 8a discontinuous elongate rib 9 which is adapted to engage in the upperpart of the channel 3 (but not the slot 4) so as to locate the lidpositively with respect to the support member. The support member 1 andpreformed lid 7 are made of a ceramic material which is capable ofwithstanding the temperature to which they will be subjected duringfusion splicing of the fibres and which will have no deleterious effecton the fibres.

When using the two-part component shown in FIGS. 1 and 2 in effecting anend-to-end fusion splice between two optical fibres, end parts of thetwo optical fibres are introduced transversely into the opposite endparts of the open-ended channel 3 in the major surface 2 of the supportmember 1 so that, at the transversely extending slot 4, the end faces ofthe optical fibres are spaced a short distance apart The preformed lid 7is then temporarily applied to the major surface 2 of the support member1 to assist in retaining the optical fibres in the channel 3 duringfusion splicing. Electrodes are then introduced into opposite ends ofthe transversely extending open-ended slot 4 and fusion splicing of theadjacent ends of the optical fibres is effected. After fusion splicingof the optical fibres has been effected, the electrodes are withdrawn,the preformed lid 7 is removed and any space in the channel 3 notoccupied by the fusion spliced optical fibres and the transverselyextending slot 4 are filled with a hot melt adhesive. Before theadhesive has set, the preformed lid 7 is re-applied to the supportmember 1 so that, on setting of the hot melt adhesive, the lid will bebonded to the support member and the two-part component will providepermanent protection for the fusion splice between the optical fibres.

The second preferred form of two-part component shown in FIG. 3comprises of a support member 11 having in one of its major surfaces 12an open ended channel 13 which has a depth substantially greater thanthe V-shaped channel 3 of the support member 1 shown in FIGS. 1 and 2.Centrally disposed between the ends of and extending transversely withrespect to the support member 11 and opening into the channel 13 aretransversely opposed apertures 14 for temporarily accommodatingelectrodes by which fusion splicing is to be effected. A preformed lid17 has on its inner major surface 18 a discontinuous elongate rib 19which is of greater depth than the rib 9 on the lid 7 shown in FIGS. 1and 2 and which engages in the upper part of the channel 13.

In the third preferred form of two-part component shown in FIG. 4, asupport member 21 has in one major cross-section and has, centrallydisposed between its ends in the major surface, a transversely extendingopen-ended slot (not shown) for temporarily accommodating electrodes bywhich fusion splicing is to be effected. A preformed lid 27 does nothave an elongate rib for engaging in the channel 24 and will be bondedto the support member 21 by a film of hot melt adhesive.

The fourth preferred form of two-part component shown in FIG. 5 issubstantially identical to the third preferred form of two-partcomponent shown in FIG. 4 with the exception that the open-ended channel33 in the major surface 32 of the support member 31 is of U-shapedcross-section.

What I claim as my Invention is:
 1. A method of effecting an end-to-endfusion splice between two optical fibres, which method comprisesintroducing end parts of the two optical fibres transversely into theopposite end parts of an open-ended channel in and extending throughoutthe length of a surface of a preformed substantially rigid elongatesupport member so that, at a position intermediate of the ends of thesupport member, the end faces of the optical fibres are spaced a shortdistance apart, the support member being made of a material which iscapable of withstanding the temperature to which it will be subjectedduring fusion splicing of the fibres and which will have no deleteriouseffect on the fibres and the support member having at said positionintermediate of its ends a transversely extending open-ended passageopening into said channel for temporarily accommodating the electrodesby which fusion splicing is to be effected; introducing the electrodesinto said transversely extending passage and fusion splicing theadjacent ends of the optical fibres; and, after fusion splicing of theoptical fibres has been effected and the electrodes have been withdrawn,substantially filling any space in the channel not occupied by thefusion spliced optical fibres and the transversely extending passagewith a curable material in a liquid or semi-liquid state and permittingor causing the curable material to set, the rigid elongate memberproviding permanent protection for the fusion splice between the opticalfibres.
 2. A method as claimed in claim 1, wherein, after any space inthe channel has been substantially filled with curable material in aliquid or semi-liquid state, a preformed elongate lid is secured to thatsurface of the support member in which the channel lies.
 3. A method asclaimed in claim 2, wherein the preformed elongate lid is made of thesame material as the elongate support member.
 4. A method as claimed inclaim 2, wherein the preformed lid is temporarily applied to saidsurface of the support member after the optical fibres have beenintroduced into the channel and before fusion splicing is effected toassist in retaining the optical fibres in the channel during fusionsplicing.
 5. A method as claimed in claim 1, wherein the preformedsubstantially rigid elongate support member is made of a ceramicmaterial.
 6. A method as claimed in claim 1, wherein the open-endedchannel in a surface of the elongate support member has a cross-sectionof substantially V-shape.
 7. A method as claimed in claim 1, wherein thetransversely extending open-ended passage is a slot in said surface ofthe support member.
 8. A method as claimed in claim 1, wherein thecurable material employed is an adhesive curable by ultra-violetradiation and, after said space has been substantially filled withcurable material, the curable material is subjected to ultra-violetradiation to cause it to set.
 9. A method as claimed in claim 1, whereinthe curable material employed is a hot melt adhesive which sets oncooling and after said space has been filled with adhesive in asemi-liquid state, the adhesive is cooled to cause it to set.
 10. Aprotected end-to-end fusion splice between two optical fibres which hasbeen effected by the method claimed in claim
 1. 11. A method for makinga protected fusion splice between two optical fibres, each said fibrehaving an end, said method comprising the steps of:providing asubstantially rigid elongate support member formed from a materialcapable of withstanding temperatures generated during fusion splicing ofthe optical fibres, said support member being characterized by alongitudinally extending open-ended channel dimensioned to receive anoptical fibre, and having a transversely aligned open-ended passageintersecting the open-ended channel; placing the optical fibres inend-to-end alignment in the channel such that the ends of the fibres areslightly spaced from one another at the intersection of the channel withthe transversely extending open-ended passage; introducing fusionsplicing electrodes into the transversely extending open ended passage;fusion splicing the ends of the optical fibres together; removing theelectrodes from the transversely extending open-ended passage; placing aflowable curable adhesive into the open-ended channel and thetransversely extending passage, such that the flowable curable adhesivesubstantially surrounds the fusion splice and portions of the opticalfibres in the channel; and curing the flowable curable adhesive suchthat the cured adhesive and the support member permanently protect thefusion splice of the optical fibres.
 12. A method as in claim 11 furthercomprising the steps of: providing a lid engageable with the channel ofthe support member when the optical fibres are disposed in the channel;and disposing the lid on the support member prior to the fusion splicingof the optical fibres.
 13. A method as in claim 12 further comprisingthe step of removing the lid prior to filling the channel and thetransversely extending passage with the flowable curable adhesive.
 14. Amethod as in claim 13 further comprising the step of replacing the lidon the support member after the step of filling the channel and thetransversely aligned passage with the flowable curable adhesive andprior to curing the adhesive, such that the adhesive secures the lid tothe support member for further protecting the fusion splice and thefibres.